Rotary anodes of x-ray tubes



June 27, i1967 B. NATTER ETAL ROTARY ANoDEs oF X-RAY TUBES Filed Aug. 26, 1964 7MOLYBDENUM WITH UP T0 50% TUNGSTEN United States Patent 3,328,626 ROTARY ANODES F X-RAY TUBES Bernhard Natter and Karl Sedlatschek, Reutte, Austria, assgnors to Schwarzkopf Development Corporation,

New York, N.Y., a corporation of Maryland Filed Aug. 26, 1964, Ser. No. 392,234

Claims priority, application Austria, Sept. 2, 1963, A 7,038/ 63 3 Claims. (Cl. 313-330) ABSTRACT 0F THE DISCLOSURE Rotary anodes of X-ray tubes have an anode core formed principally of,a molybdenum-tungsten alloy and an adhering target layer formed principally of tungsten. The molybdenum-tungsten alloy of the anode core consists principally of molybdenum alloyed with 2 to 10% of tungsten and it may contain up to 50% tungsten, all proportions given by weight. The moly-bdenum-tungsten alloy of lthe anode core may also contain alloy additions of rhenium, niobium and osmium, with rhenium up to 30% by weight, being primarily suitable for such anode core.

This invention relates to X-ray tubes operating with rotary anodes such as described in U.S. Patent 3,136,907 and more particularly to the rotary anodes of such tubes.

Because of the critical operating load conditions, such anodes have previously been formed of tungsten and were made exclusively of tungsten powder, compacted into rods, sintered, rolled into plates and then stamped and forged to the required nal anode shape.

Tungsten has proved very eicient as a material for X-ray anodes owing to its high melting point and high atomic number. In order to reduce the requirement of tungsten in X-ray an-odes to a minimum and to facilitate its shaping it has been previously proposed to make the core of the rotary anodes of molybdenum land to provide the molybdenum core with a layer of tungsten in the area the electrons impinge on the anode. Such anodes also have a lower weight 4than those made of solid tungsten. The present invention represents a further improvement in this type of anode, According to the invention, the core of the anode consists mainly of molybdenum alloyed primarily with tungsten, as well as Itantalum, niobium, rhenium and osmium. An addition of as little as 0.5% tungsten results in an increase in hot strength, recrystallization temperature and inhibition of grain growth of the anode.

This forms a primary object of our invention.

A further object of the invention also includes embodiments in which the molybdenum-tungsten alloy of the anode core is alloyed with other refractory metals. Rhenium in quantities of up to 30% is primarily suitable for this purpose. (In the specification and claims all percent proportions are given by Weight.)

The foregoing and other objects of the invention will be more fully understood from the following description of exempliications thereof, reference being had to the accompanying drawings, wherein:

FIG. 1 is a diagrammatic view of one example of an X-ray tube operating with a rotary anode of the invention; and

FIG. 2 is an enlarged elevational view, partially in cross-section of the anode of FIG. 1.

FIGS. 1 and 2 show an example of [an X-ray Itube operating with a rotary anode of the invention. The glass envelope contains, in a very high vacuum, the cathode system 2 with the filament or filaments 3 `in the concentrating member located opposite to the conical portion of anode disc 7 which is connected to and rotated by a rod 6 of the motor rotor 5. By applying a high tension voltage so that the cathode is negative andthe anode is positive, a beam of electrons emitted from the incandescent filament 3 bombard the focal target seat 10 of the anode 7 and produce X-radiation at this point. The electron beam energy is transformed almost entirely into heat which, rapidly heats the focal seat of target 10 and the whole mass of the anode 7. The tube structure above described is of a known type and the rate at which successive exposures may be made, or at which exposures may be made following a viewing, depends upon the thermal capacity of, and the speed of cooling from the anode disc 7.

As previously pointed out, the core of the anode 7 consists mainly of molybdenum alloyed with another refractory metal. Suitable alloying additions are primarily tungsten, as well as tantalum, niobium, rhenium and osmium. An addition of as little as 0.5% tungsten results in an increase in hot strength, recrystallizationtemperature and an inhibition in grain growth of the anode core 7.

An increase in the proportion of tungsten in the anode core also has the effect of reducing the diierences in thermal expansion between the core and the tungsten target layer 10, which also reduces the risk of deforma- -tion of the anode and its target due to the heating during operation. Additions of 2 to 10% tungsten have proved suitable in practice. It was found, however, tha-t even higher additions to tungsten up to 50% by weight appear economically feasible as compared with unalloyed molybdenum cores.

Other additions can also be used, for instance, small quantities of alkali silica-tes or stable oxides in order to achieve a further increase in the recrystallization temperature of the anode.

Conventional methods can be used for producing X- ray anodes in accordance with the invention. For example, the molybdenum-tungsten part and the tungsten part can be made separately by powder-metallurgical methods and the two parts can then be joined and given their final shape by precision forging. Alternatively, the entire anode with its target can be pressed from powder of the corresponding compositions then sintered and the iinal shape imparted by suitable methods such as rolling, stamping, forging or other suitable operations.

Although we have described preferred embodiments of the invention, many variations and modifications will be obvious to those skilled in the art, and the claims shall not be limited to the specific disclosure herein.

We claim:

1. An X-ray tube having a rotary metallic anode body with an exposed target area and electron beam means for producing an electron beam impinging on said target area and causing emission of X-rays therefrom,

said anode body having an anode core consisting principally of a molybdenum alloy containing 2 to 10% 3 4- by weight of tungsten material and an adhering target References Cited layer exposed to said electron beam consisting prin- UNITED STATES PATENTS CiPaHY 0f tungsten 1,153,290 9/1915 Coolidge 313-330 2. An X-ray tube as clarrned in claim 1, 5 2,125,896 3/1938 Driggs et aL 3,13 330 said anode core consisting essentially Of molybdenum 2,863,083 12/ 1958 Schram 313-330 alloy with 4 to 10% by weight of tungsten. 3,136,907 6/ 1964 Kieffer et al. 313-330 3. An X-ray tube as claimed in claim 1, n the molybdenum-tungsten alloy of said anode core con- JOHN W' HUCKERT Pr'mmy Exammer taining therewith 0 to 30% -by Weight of rhenium. 10 A. L. BRICH, A. J. IAMES,'Assstant Examiners. 

1. AN X-RAY TUBE HAVING A ROTARY METALLIC ANODE BODY WITH AN EXPOSED TARGET AREA AND ELECTRON BEAM MEANS FOR PRODUCING AN ELECTRON BEAM IMPINGING ON SAID TARGET AREA AND CAUSING EMISSION OF X-RAYS THEREFROM, SAID ANODE BODY HAVING AN ANODE CORE CONSISTING PRINCIPALLY OF A MOLYBDENUM ALLOY CONTAINING 2 TO 10% BY WEIGHT OF TUNGSTEN MATERIAL AND AN ADHERING TARGET LAYER EXPOSED TO SAID ELECTRON BEAM CONSISTING PRINCIPALLY OF TUNGSTEN. 